Hello. I own a 1987 Cal-x fun spa. It was built by Leisure Life spa in 1987. Model #50. Serial #179081. On the heater box it says Cal-x fun spa model14-L010CL. It runs on 120 volts. There is an independent 20 amp breaker for it with a new 20 amp gfic outlet. I have replaced the pressure switch, thermostat and top control panel, high limit switch and o-ring gaskets on the shut off valves. The shell is in great shape and so is the tub. I need to replace the skimmer flap-door. The cover is old and is coming unstitched on one seem.

The problem I was having is that the contactor was chattering when in low speed. It doesnt do it when the jets are on. Is it grounding out somewhere or is the heater bad? Its like it is trying to shut off or something. So I can not run the spa. The spa was originally a gift, but after all of the repairs and cost of moving it, it doesnt seam as much as a gift.
Please help. I really want to use the spa and I am frustrated

generally, contactors are only used for the heating element, and relays for the pump motors. Most often cause of chattering is due to low voltage. Check to see if your contactor is indeed set up for 120V (and not 240 like I suspect) and that you are getting full 120V to it when it is trying to energize.